Subject: swap overflows if flag VIRT_MEM is set
From: Andreas Piper <piper@hrz.uni-marburg.de>
Date: Fri, 31 Aug 2007 13:40:28 +0200

Hello list,

when I set the flag VIRT_MEM in /etc/vservers/<vservername>/flags,
the vserver seems to consume very fast all of its swap-space, as observed 
with 'free' inside the vserver. I am running Horde-3.1.4 under apache-2.2.3 
with php-5.2.0 on the vserver, every reload of the Horde-webpage takes some 
400 MByte from the swap (and nothing from Mem, which remains nearly 
completely free). As a result, I get 'out of memory'-errors very soon.

The master-server does not see the change in used swap-space at all, 'free' on 
the master shows 0 swap-usage, even if the vserver shows 3.5GByte of 
swap-usage.

I am using vserver version vs2.0.2wcr on Linux version 2.6.17.13 under Debian 
etch, and util-vserver version 0.30.212-1

The content of /etc/vservers/<vservername>/flags is:
sched_prio
virt_mem
virt_uptime
virt_load
virt_cpu

When I leave out the VIRT_MEM flag, the swap-space on the vserver remains 
empty, and Memory-usage increases by reasonible values, but 'vserver-stat' 
still shows a VSZ of 15.9+ (whatever that means).

Does it help to just leave out the VIRT_MEM-flag, or is there some real memory 
management problem behind this?

Thanks for any help,
Andreas